add a testing experience

git-svn-id: http://svn.zope.org/repos/main/zc.buildout/trunk@115987 62d5b8a3-27da-0310-9561-8e5933582275

DEVELOPERS.txt

@@ -9,3 +9,9 @@ When you're developing buildout itself, you need to know two things:
 
 - Don't bootstrap with ``python bootstrap/bootstrap.py`` but with ``python
   dev.py``.
+
++1 for testing:
+
+- You should have specific python versions at specific locations or
+  PYTHONx.x environment variables pointing to those
+  See zc.buildout testing.py, def find_python(version)
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